1. Field of the Invention
The present invention relates to a touch screen, a touch panel, and a display device having the same.
2. Description of the Background Art
In related art, a touch panel that detects touch of a pointer such as a finger and specifies coordinates of a touch position has attracted attention as excellent interface means. In this touch panel, various schemes such as a resistive scheme and a capacitive scheme have been discussed and commercialized.
As a type of touch panel using the capacitive scheme, a touch panel using a projected capacitive scheme discussed in Japanese Patent Application Laid-Open (Translation of PCT Application) No. 9-511086 (1997) is known. In the touch panel of the projected capacitive scheme, even when a front side of a touch screen having a touch sensor embedded therein is covered with a protective plate such as a glass plate having a thickness of a few mm, touch of, for example, a finger to the protective plate can be detected. Such a touch screen has excellent robustness, touch can be detected even when a user wears a glove, and the touch screen has a long life with no movable parts, and thus various technologies have been proposed based on these advantages.
For example, a touch screen constituting the touch panel discussed in Japanese Patent Application Laid-Open (Translation of PCT Application) No. 9-511086 (1997) includes a first series of conductor elements formed of a thin conductive film, and a second series of conductor elements formed on the first series of conductor elements via an insulating film, as detection wirings (detection electrodes) for detecting capacitance. Further, a plurality of intersections are formed without electrical contact between the conductor elements. According to technology discussed in Japanese Patent Application Laid-Open (Translation of PCT Application) No. 9-511086 (1997), capacitance formed between a pointer, such as a finger, and the conductor element, which is the detection wiring, is detected by a detection circuit, so that position coordinates of a position touched by the pointer can be specified. Further, a touch position between the conductor elements can be interpolated by relative values of detected capacitances of one or more conductor elements.
A touch screen constituting a touch panel discussed in Japanese Patent Application Laid-Open No. 2010-61502 includes detection column wirings and detection row wirings, and each of the wirings is formed as a metal wiring having a zigzag pattern in which the wiring is repeats a zigzag shape with inclined portions inclined at 45° in column and row directions. According to the technology discussed in Japanese Patent Application Laid-Open No. 2010-61502, high wiring density can be obtained and touch detection sensitivity can be improved without increasing parasitic capacitance between the detection wirings.
A touch screen constituting a touch panel discussed in Japanese Patent Application Laid-Open No. 2010-97536 includes detection column wirings and detection row wirings formed in a zigzag pattern, similar to the touch screen of Japanese Patent Application Laid-Open No. 2010-61502, and a wiring between the detection column wiring and the detection row wiring.
In Japanese Patent Application Laid-Open (Translation of PCT Application) No. 2003-526831, a detection scheme generally called a mutual-capacitance detection scheme has been discussed. Specifically, a key matrix discussed in Japanese Patent Application Laid-Open (Translation of PCT Application) No. 2003-526831 includes an array of a plurality of driving/receiving electrode pairs, and detects, as a charge amount, a change in coupling capacitance (mutual electrode capacitance) according to an electric field change between electrodes generated due to contact of a pointer, such as a finger, with a substrate.
A capacitance-based touch detection device discussed in Japanese Patent Application Laid-Open (Translation of PCT Application) No. 11-505641 (1999) includes an electrode array including an X electrode and a Y electrode. Mutual-capacitance between the X electrode and the Y electrode is detected by a capacitance measurement circuit. Also, an output voltage change indicating the measured capacitance is determined according to the mutual-capacitance, known reference capacitance, and a known driving voltage change.
According to the technologies discussed in Japanese Patent Application Laid-Open No. 2010-61502 and Japanese Patent Application Laid-Open No. 2010-97536 described above, high wiring density can be obtained without increasing inter-wiring capacitance (hereinafter, “capacitance between row and column wirings”) formed between the detection column wiring and the detection row wiring. Further, the detection wirings arranged in a rectangular shape have advantages such as an easy coordinate interpolation process based on a detection result or high linearity of coordinates obtained by the interpolation process (particularly, in an oblique direction), as compared to detection wirings arranged in a diamond chain shape.
Meanwhile, capacitance between row and column wirings changed according to presence or absence of touch of a pointer, such as a finger, to a touch screen is closely related to detection sensitivity depending on detection methods. For example, according to the mutual-capacitance detection scheme discussed in Japanese Patent Application Laid-Open (Translation of PCT Application) No. 2003-526831, a high change in the capacitance between row and column wirings (a change in an electric field between electrodes) according to the touch of the pointer, such as the finger, can provide high detection sensitivity.
However, for example, in a configuration in which capacitance (electric field coupling) between a bundle of wirings in a column direction and a bundle of wirings in a row direction is high, like a configuration in which the detection method discussed in Japanese Patent Application Laid-Open No. 2010-97536 is applied to the touch screen discussed in Japanese Patent Application Laid-Open No. 2010-61502, it is difficult for a change in an electric field between the detection column wiring and the detection row wiring according to touch of the pointer, such as a finger, i.e., a change in capacitance between row and column wirings, to occur. Accordingly, when the mutual-capacitance detection scheme is applied in such a configuration, the touch detection sensitivity is low.